Ok, It's similat the TV' room whitn Lynn, don't work but kork with she is in her room.Buy the oldest sister a new dress, at night when she comes in your room offer to do a photoshoot with her, photoshoot will be at 14:00 at the pool. Afterwards, an event with the two younger sisters will trigger where they get upset she can do nude shoots but they can't. Go to the dining room at 19:00 and then the next day you can go in the bathroom at 17:00 (15:30 is incorrect in game, it's at 17:00 or whenever both are in the bathroom).
Thnks.